The touch panel may be classified into resistance type touch panel, capacitance type touch panel, ultrasonic type touch panel, and infrared type touch panel, etc., according to work principles. Take the capacitance type touch panel as an example. Its major process includes the step of depositing an antimony tin oxide (ATO) film and silver paste wires on the glass. The capacitance type touch panel benefits from high stability, good transmittance, and high surface hardness, but its cost is high and its process is complicated. As for the resistance type touch panel, it is mainly made of an indium tin oxide (ITO) conductive film and an indium tin oxide conductive glass. The resistance type touch panel benefits from lower cost and simpler structure, but has inferior transmittance and surface hardness to the capacitance type touch panel. The ultrasonic type touch panel obtains coordinate of a certain position by emitting ultrasonic wave and computing the strength of the received signal. The infrared type touch panel works on the light barring principle. Infrared emitting and receiving devices are disposed on the periphery of the panel, and the light signal would be barred when an object touches the panel. The coordinates of the object could be obtained by analyzing the signal received by the receiving device.
FIG. 1 shows a known apparatus 100 for detecting position applied in an infrared type touch pane. The apparatus 100 includes a rectangular frame 110, infrared sources 131-137 and 141-147, and light receivers 151-157 and 161-167. The light receivers 151-157 are configured to receive light emitted from the infrared sources 131-137 respectively, and the light receivers 161-167 are configured to receive light emitted from the infrared sources 141-147 respectively. When a finger or other object 120 is set in a certain position within the frame 110, the light receivers 163 and 164 cannot receive light from the light sources 143 and 144, and the light receivers 153 and 154 cannot receive light from the light sources 133 and 134. The x-coordinate of the object 120 within the frame 110 can be determined by the locations of the light receivers 153 and 154, and the y-coordinate of the object 120 within the frame 110 can be determined by the locations of the light receivers 163 and 164.
In the apparatus 100 shown in FIG. 1, the light sources are disposed on the two edges of the rectangle which are perpendicular to each other, and the corresponding light receivers are disposed on the remaining two edges for detecting the coordinate of the object within the frame. However, the configuration of the apparatus 100 shown in FIG. 1 is only suitable for the rectangular frames, but not suitable for the frames of shapes other than rectangle, such as circle or other irregular shapes.
Consequently, it is necessary to provide an apparatus for detecting the position of objects on the panel, which can be applied to panels of arbitrary shapes.